Thermal relay



Jan. 22, 1929.

A. J. MOTTLAU THERMAL RELAY 2 sheets-sheet Filed Oct. 9, 1926 WITNESSES:3. 8.9%

AII'TORNEY Jan. 22, 1929. 1,699,802

A. J. MOTTLAU THERMAL RELAY Filed Oct. 9, 1926 2 Sheets-Sheet 2WITNESSES: INVENTOR 24 ATTORNEY Patented Jan. 22, 1929.

UNITED STATES PATENT OFFICE.

AUGUST J. MOTTLAU, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTING-HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

THERMAL RELAY.

Application filed October 9, 1926. Serial No. 140,568.

My invention relates to protective relays for electric translatingdevices and particularly to thermally actuable relays.

An object of my invention is to provide an electric control switch thatshall be operable by a plurality of current-conducting bimetallicelements that are energized in accordance with the current flowing in acircuit to be controlled.

Another object of my invention is to provide a plurality of integral,parallel, spaced bimetallic elements that shall be operable as a unit inresponse to a predetermined current condition therein to actuate acontrol circuit.

Another object of my invention is to provide a thermal relay that shallbe operable over a wide range of current conditions in a circuit to beprotected.

Another object of my invention is to provide a thermal relay that shallautomatically return to its operative position after a relatively shortperiod of time after being actuated to an inoperative position.

In practicing my invention, I provide a plurality of slotted bimetallicelements that are so disposed in parallel planes, one above another thatthey combine to produce a unilied motion when they are thermallyenergized from an electric circuit. The elements are electricallyconnected together in seriescircuit relation. In the preferredembodiment of my invention, I propose to make the bimetallic elementsfrom a single sheet of material.

Means are provided for holding a central portion of the bimetallicelements in a relatively fixed position with respect to the endsthereof. A control switch is disposed in operative relation to thebimetallic elements and is actuated thereby through a plurality ofintersecting links that are operated wit 1 a scissorlike motion, Thecontrol switch may be moved away from, or towards, the actuatingmechanism in accordance with the condition of the bimetallic elementsthat is selected as desirable.

In the accompanying drawings, Fig. 1 is a plan view of the deviceembodying my invention.

Fig. 2 is a view, partially in section and partially in side elevation,of the device illustrated in Fig. 1, taken on the line 11-11 thereof.

Fig. 3 is a to plan view of a pair of lever members embo ied in myinvention,

Fig. 4 is a view, similar to Fig. 2, but showing the relay in anactuated position.

Fig. 5 is a top plan view of a detail embodied in the device illustratedin Figs. 1, 2 and 3, and

Fig. 6 is an end view of the detail illustrated in Fig. 5.

In the drawings, a thermally actuable relay 11 comprises a base member12, a thermo-responsive means 13, a switch 14 and an actuating mechanism15. The thermoresponsive means 13 comprises a plurality of parallel,spaced-apart bimetallic members 16, 17 and 18. Each of the bimetallicelements 16, 17 and 18 has a longitudinallyextending slot or aperture 19(see Fig, 5) and they are electrically connected from opposite sides bynarrow integral metallic connecting portions 21 and 22. The members 16,17 and 18 and the connecting portions 21 and 22 are separated from eachother by suitable insulating strips 23.

The thermally-responsive means 13 is supported by a block of insulatingmaterial 2-1 that is suitably secured to the base member 12 h bolts 25and 26. The ends of the bimetallic portion 18 of the thermo-responsivemeans 13 have mounted thereon a plurality of angle pieces 27 that aresecured thereto by rivets 28. The pieces 27 are provided with alignedapertures 29 to receive a pin 31.

The actuating mechanism 15 comprises a pair of levers 32 and 33 that arepivotally secured in operative engagement with the members 27 by thepins 31. The lever 33 (see Fig. 3) comprises two alined portions 34 and35 that are joined together in operative relation by a pair of metalsupporting members 36 secured to the sides thereof between which anaperture 37 is formed. The members 36 are secured to the members 34 and35 by rivets 38. The member 32 extends through the aperture 37 in suchman ner that the members 32 and 33 intersect and are, therefore,disposed in substantially the same plane.

An insulating block 39 is supported by the bolts 25 and 26 in apredetermined position by nuts 41 and 42.

The switch 14 is secured to the block 39 by a pair of bolts 43 and 44and comprises a resilient metal frame 45 having a pair of apertures 46and 47 punched therein to provide a bridging member 48 which extendslongitudinally of the frame 45. The bolts 43 and 44 extend through thesides of the frame 45 to secure the switch to the block 39. The frame 45is provided with deformed end portions 49 of such dimensions and shapethat the apertures 46 and 47 are substantially shorter than the bridgingmember 48. The bridging member 48 comprises a pair of upwardly curvedend portions 51 and an intermediate downwardly deflected portion 52. Acontact member 53 is mounted on the bridging member 48 and is adapted toengage a contact member 54 that is mounted on the insulating block 39.

The contact member 54 is maintained in position on the insulating block39 by a bolt 55 which serves as one terminal for the control switch 14.A bolt 56, which forms a second terminal for the switch 14, extendsthrough the block 39 and registers with one side of the frame 45. Theends of the switch 14 are provided with spaced-a art depending members57 of L-shape, w ich members have aligned apertures 58, through whichpins 59 extend. The members 57 are secured to the frame 45 by rivets 60.

The members 32 and 33 are provided with notched end portions 62 whichextend between the depending members 57 to rest on the pins 59.

When such bending force is applied to the members 57 of the switch 14that the right and left-hand ends thereof tend to rotate incounter-lockwise and clockwise directions, respectively, the bridgingmember 48 is stressed until the portion 52 thereof reaches a state ofunstable equilibrium. If the bending force is increased still further,the intermediate portion 52 will be caused to deflect to a state ofstable equilibrium, with a sudden snap-motion, thereby disengaging thecontact member 53 from the contact member 54. The portion 52 will remainin its deflected position so long as the bending force is applied, but,in the event it is removed, the portion 52 will return to its normalposition, as illustrated in Fig. 2, with a snap motion.

The bending force referred to above is applied by means of thebimetallic means 13 and the intersecting members 32 and 33. When thebimetallic means 13 is heated by an electric current flowing therein,the free ends thereof curve upwardly. (See Fig. 4).

The switch 14 may be moved vertically towards or away from thebimetallic means 13 by turning the nut 41, which operatively engages theblock 39 and the bolt 25, in the proper direction. As the switch ismoved upwardly, the notched end portions 62 of the members 32 and 33slide freely on the pins 59.

When the bimetallic members 16. 17 and 18 are connected in aheavy-current circuit by means of a pair of terminal members 63 and 64,the heating produced therein by the resistance losses incidental tocurrent traversing the conductors causes the free ends thereof to curveupwardly, substantially as illustrated in Fig. 4 of the drawings. As theelements curve upwardly, the members 32 and 33 are caused to moveupwardly and laterally, but in opposite directions, until the notchedportions 62 thereof register with the pins 59, whereby bending momentsare applied to the members 57. When the bimetallic members 16, 17 and 18have curved upwardly until the members 57 and 58 of the switch 14 havebeen bent outwardly and upwardly, as indicated in Fig. 4 of thedrawings, contact member 53 will have become disengaged from the contactmember 54. I have found, by experiment, that the switch functions verysatisfactorily when actuated by the thermal means 13 and the intersectmgmembers 32 and 33 associated therewil h. in the manner hereinbeforedescribed.

The switch 14, as illustrated in the drawgs, specifically constitutes nopart of my invention, as it is described and claimed in my Patent No.1,668,974 issued May 8, 1928 and assigned to the Westinghouse Electricand Manufacturing Company.

The terminal members 55 and 56 of the switch 14 may be assumed to beconnected in circuit with the holding coil of a circuit interrupter, adevice which controls a heavycurrent circuit in which the bimetallicmeans 13 may be connected. When the current traversing the bimetallicmeans 13 has reached a predetermined value, the expansion thereo asillustrated in Fig. 4 of the drawings, will cause disengagement of thecontact members 53 and 54 to de-energize the control circuit, with theconsequent deenergization of the heavy-current circuit. When thebimetallic means 13 has cooled sufliciently to assume the positionillustrated in Fig. 2 of the drawings, the switch 14 will automaticallyreclose itself and assume the osition illustrated in Fi 2 of thedrawings. he heavy-current circuit will then be ready to be energizedfor further service.

If it is desirable that a relatively large current shall traverse thebimetallic means 13 before the switch 14 is actuated to the positionillustrated in Fig. 4, the latter is moved upwardly by the adjusting nutmember 41. It is, therefore, evident that the bimetallic members 16, 17and 18 must be heated to a higher temperature before the notched portionof the members 32 and 33 will engage the pins 59 of the switch 14.

If it is desirable that a relatively small current shall be effective toactuate the control switch 14, the adjusting screw 41 is turned untilthe switch 14 has been lowered to the desired position. It is,therefore, evident that the bimetallic means need not be heated to sohigh a temperature as referred to above to actuate the switch 14.

The bimetallic means 13, as illustrated in the drawings, may be made asingle flat sheet of bimetallic material by punching the apertures 19therein and by cutting away material from the ends longitudinallythereof so that the members 16, 17 and 18 formed thereby are joined bythe intervening strips 21 and 22, and by so folding the flat bimetallicsheet, after the necessary punching operation, that the correspondingmetals of the sheet extend in the same direction, as illustratedparticularly in Fig. 6 of the drawings, the heating of the elements willresult in a deflection thereof in the same direction. The ends of thebimetallic members 16, 17 and 18 may be maintained in spaced relation bysuitable electric insulating spacing members 66.

Since the bimetallic elements 16, 17 and 18 are traversed by electriccurrent, they respond very quickly to changes in current andparticularly when a sudden abnormal value of current flows therethrough.This responsive feature would not be available (when the current changessuddenly to an abnormally large value) if the bimetallic elements wereenclosed by an independent resistor member, because the air between theresistor and the elements would act as a thermal insulator. It follows,also, that the elements 16, 17 and 18 will cool quickly because thesurrounding air may circulate freely between them, thereby affording aquick reset of the switch 14 after it has been actuated to the positionillustrated in Fig. 4.

By my invention, I provide a thermal rela that is simple inconstruction, that has re atively few parts, and that is positive inoperation. In general, I provide a bimetallic thermally-responsive meansthat is adapted to be heated by an electric current traversing it. Thebimetallic means actuates a control switch by means of asimpleioperating mechanism when a predetermined .value of current hastraversed it for a predetermined length of time. The control switch maybe moved away from, or towards, the bimetallic elements to thus providea relatively wide range of current conditions to which the currenttraversed means may be subjected before actuating the control switch.

Various modifications may be made in the device embodying my inventionwithout departing from the spirit and scope thereof.

I desire, therefore, that only such limitations shall be placed thereonas are imposed by the prior art and the appended claims.

I claim as my invention:

1. The combination with a control switch comprising an aperturedresilient frame and a bridging member extending across the aperture, andthermo-responsive means, of a plurality of intersecting membersoperatively engaging the frame and said thermo-responsive means foractuating said frame to cause deflection of said bridging member uponmovement of the thermo-responsive means.

2. In a switch structure, a quick-break control switch, an elongatedthermo-responsive bimetallic strip, and a plurality of intersectingmembers operatively engaging said bimetallic strip and control switchfor actuating said switch when the bimetallic strip has reached apredetermined thermal condition.

3. In a switch structure, a quick-break control switch, an elongatedthermo-res onsive bimetallic strip, and a plurality 0 in dependentmembers operatively engaging said bimetallic strip and control switchfor actuating said switch when the bimetallic strip has attained apredetermined thermal condition.

4. In a switch structure, a control switch having contact memberstherefor normally biased into an engaged position, a plurality ofserially connected spaced-apart bimetallic strips, and a pair ofindependent intersecting members disposed in operative engagement withthe ends of said bimetallic strips and said switch for actuating thecontact members to a disengaged position whenthe bimetallic members havereached a predetermined thermal condition.

5. In a thermal relay, the combination with a circuit controlling devicecomprising a metal plate having an aperture therein and. a bridgingmember extending across the aperture, of a bimetallic unit and a pair ofindependent intersecting members disposedin parallel planes, actuated bythe bimetallic unit to apply deflecting thrusts to the ends of the platefor actuating the bridging member.

6. In a thermal relay, the combination with a switch, and an actuatingmechanism therefor, of thermall responsive means for actuating said mecanism, comprising a plurality of spaced-apart apertured bimettalicmembers disposed one above the other and adapted to deflect in the samedirection, said members being held fixed at the central portions thereofand being integrally connected from opposite sides substantially at saidcentral portions.

7. The combination with apertured elongated bimetallic members, and apair of inependent intersecting members, each of said members having oneend thereof pivotally secured to op osite ends of said himetallicmembers, 0 a. switch member su ported in operative engagement with t eother ends of said intersecting members for operating the switch when apredetermined thermal condition exists in the bimetallic member.

8. The combination with an a rtured elongated bimetallic member, a pairof independent intersecting members, each of sald members having one endthereofdpivotally mounted at opposite ends of sai bimetallic member,aswitch member supported in operative engagement with the other ends ofsaid intersecting members, of means for movin said switch away from ortowards sai intersecting members in accordance with a predeterminedthermal condition at which said bimetallic member shall be effective tooperate the switch.

In testimony whereof, I have hereunto subscribed my name this 2nd day ofOctober, 1926.

AUGUST J. MOTTLAU.

